A communication system operates to provide for the communication of data between communication stations of a set of communication stations. At least one of the communication stations of the set of communication stations forms a sending station. And, at least another of the communication stations of the communication system forms a receiving station. Data is communicated by the sending station to the receiving station by way of a communication channel. If necessary, the sending station converts the data into a from to permit its communication upon the communication channel, and the receiving station operates to detect the data communicated upon the communication channel and to recover the informational content thereof.
Many different types of communication systems have been developed and deployed and many different communication services are effectuable by way of appropriate ones of the communication systems. As advancements in communication technologies shall likely permit the development and deployment of additional types of communication systems, additional communication services shall likely become available. The need for ready access to communication systems, already pervasive, shall likely, therefore, become even more so in the future.
A radio communication system is an exemplary type of communication system. In a radio communication system, the communication channel upon which data is communicated by a sending station to a receiving station is formed of a radio channel defined on a radio link extending between the sending and receiving station. Because data is communicated between the sending and receiving stations upon a radio channel, the need to interconnect the sending and receiving stations by way of a wireline connection is obviated. And, free of the need to interconnect the sending and receiving stations by way of fixed connections, communications by way of a radio communication system are effectuable at, and between, locations at which communications by way of a wireline communication system are not possible. And, a radio communication system is implementable as a mobile communication system in which one or more of the communication stations is permitted mobility.
A cellular communication system is a type of radio communication system. The networks of cellular communication systems have been installed to encompass significant portions of the populated areas of the world. Telephonic communications are effectuable by way of a cellular communication system. Telephonic communications of both voice and data communication services are effectuable by way of a cellular communication system pursuant to communication sessions between the communication stations. Advanced generations of cellular communication systems are permitting of the effectuation of data intensive communication services in which content is communicated between communication stations.
The increasingly data-intensive nature of many communication services taxes the capacities of cellular communication systems, as well as other bandwidth-constrained communication systems. That is to say, bandwidth allocations in cellular, as well as many other, communication systems are limited. And, the communication capacities of such communication systems are regularly limited by the allocations of the bandwidth thereto. Efforts are made, therefore, to utilize, as efficiently as possible, the allocated bandwidth, allocated for use by the communication system.
When the communication system forms a multi-access communication system, i.e., permits multiple communication sessions between multiple sets of communication stations concurrently to be performed, various channel differentiation techniques are utilized. Code-division, multiple-access and frequency division multiplexing techniques are, for instance, utilized.
In a communication system that utilizes code-division, multiple-access (CDMA) techniques, spreading codes are used by which to code data by different ones of the communication stations. Spreading codes are regularly called the codewords of a code with good correlation properties, e.g., the codewords of a Hadamard code are called spreading codes. Channel differentiation is provided by the spreading codes that code the data that is communicated. Conventionally, the spreading codes that are used are mutually orthogonal. When the spreading codes are orthogonal, the resultant coded data coded by the different ones of the spreading codes do not interfere with one another when synchronously communicated.
Analogously, some communication systems that utilize frequency division multiplexing techniques utilize orthogonal frequency division multiplexing (OFDM) techniques in which the channels are defined in manners to be mutually orthogonal with one another. Data communicated upon the orthogonal channels, in single-path conditions, do not interfere with one another. Cellular, and other radio, communication systems, for instance, are sometimes implemented as CDMA or OFDM communication systems.
Definition of the channels to be mutually orthogonal with one another, however, limits the number of channels that can be defined within a given bandwidth. By removing the orthogonality requirement, additional channels, within a given bandwidth, can be defined. However, when the channels no longer are orthogonal, data communicated upon different ones of the channels interfere with one another. If the levels of interference are not significant, the informational content of the concurrently communicated data is recoverable, in spite of the interference introduced by the concurrently communicated data. If a manner could be found by which to provide codes, although not formed of codewords that are mutually orthogonal, that exhibit low levels of cross-correlation among the codewords of the codes, more efficient utilization of the bandwidth allocated to a communication system would be possible.
What is needed, therefore, is a manner by which to design codes that, while not mutually orthogonal, exhibit low levels of cross-correlation between the codeword pairs of each code.
It is in light of this background information related to multi-access communication systems that the significant improvements of the present invention have evolved.